1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display device and a fabricating method thereof wherein the liquid crystal display device is driven with a magnetic field.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls an electric field applied to a liquid crystal cell to modulate a light incident to the liquid crystal cell, thereby displaying a picture. The liquid crystal display may be largely classified as a vertical electric field system and a horizontal electric field system based on a direction of the electric field driving the liquid crystal.
The vertical electric field system includes an upper substrate and a lower substrate vertically opposed to each other along with a pixel electrode and a common electrode that are also vertically opposed to each other. In the vertical electric field system, an electric field is applied to the liquid crystal cell in a vertical direction by a voltage applied to the electrodes. The vertical electric field system has a drawback in that although it can assure a relatively wide aperture ratio, it has a narrow viewing angle. A typical liquid crystal mode of the vertical electric field system is a twisted nematic (TN) mode which is used for a majority of liquid crystal display devices.
As shown in FIG. 1A and FIG. 1B, the TN mode has liquid crystal molecules 13 positioned between the upper glass substrate 14 and the lower glass substrate 12. An upper polarizer 15 having a specific direction of light transmitting axis is attached onto a light output face of the upper glass substrate 14 while a polarizer 11 at a light transmitting axis perpendicular to the light transmitting axis of the upper polarizer 15 is attached onto a light incidence face of the lower glass substrate 12. Further, the TN mode has a transparent electrode provided at each of the upper glass substrate and the lower glass substrate, and an alignment film for establishing a pre-tilt angle of the liquid crystal.
Herein, operation of the TN mode will be described assuming it to be a normally white mode.
A local light axis (director) of the liquid crystal molecules is continuously twisted at 90 degrees between the upper glass substrate 14 and the lower glass substrate 12 at an inactive state in which a voltage is not applied to the upper glass substrate 14 and the lower glass substrate 12. During the inactive state, polarization characteristics of the line polarization input via the polarizer 11 of the lower glass substrate 12 is changed to fail to pass through the polarizer 15 of the upper glass substrate 14. On the other hand, during an active state in which a voltage is applied to the upper transparent electrode and the lower transparent electrode and an electric field is applied to the liquid crystal 13 by the voltage difference, a light axis of the center portion of the liquid crystal layer becomes parallel to the electric field and the twisted structure is released. A line polarization input via the polarizer 11 keeps its polarization characteristic as it is while going through the liquid crystal layer, and passes through the polarizer 15 of the upper glass substrate 14.
However, the TN mode has a drawback in that, since a contrast ratio and a brightness variation according to a viewing angle, it is difficult to realize a wide viewing angle.
A horizontal electric field system is an in plane switching (IPS) mode in which an electric field between the electrodes provided on the same substrate is formed and the liquid crystal molecules are driven with the electric field.
As shown in FIG. 2, in the IPS mode, a first metal electrode 21 and a second metal electrode 22 are provided in such a manner as to cross each other and an in plane driving of a liquid crystal 23 is made by an electric field applied between the metal electrodes 21 and 22, thereby realizing a wide viewing angle.
However, the IPS mode has a drawback in that it has a low aperture ratio due to the first and second metal electrodes 21 and 22.